Fill a large mason jar with the unwashed sour cherries, keeping the stones intact to prevent mushiness.
Fill the jar to the brim with sugar.
Fill the jar to the brim with gin.
Wait 3 to 4 months for the sugar to completely dissolve.
To serve, place 3 to 4 cherries and 3 to 4 teaspoons of the gin liqueur in a champagne glass and fill with dry sparkling wine.
Optional: For a more elegant presentation, pour the cherries and sparkling wine into the glass first, then carefully pour the liqueur over the back of a spoon to keep the red liquid at the bottom.